Writes from I2C bus often fail when testing the i2c-designware-slave.c
with the slave-eeprom backend. The same writes work correctly when
testing with a real 24c02 EEPROM chip.
In the tests below an i2c-designware-slave.c instance with the
slave-eeprom backend is configured to act as a simulated 24c02 at
address 0x65 on an I2C host bus 6.
1. i2cset -y 6 0x65 0x00 0x55
Single byte 0x55 write into address 0x00. No data goes into simulated
EEPROM. Debug prints from the i2c_dw_irq_handler_slave():
0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x714 : INTR_STAT=0x204
0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
2. i2ctransfer -y 6 w9@0x65 0x00 0xff-
Write 8 bytes with decrementing value starting from 0xff at address 0x00
and forward. Only some of the data goes into arbitrary addresses.
Content is something like below but varies:
00000000 f9 f8 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000050 00 00 00 00 00 00 ff fe 00 00 00 00 00 00 00 00 |................|
000000f0 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fb fa |................|
In this case debug prints were:
0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x714 : INTR_STAT=0x204
0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x510 : INTR_STAT=0x0
Both cases show there is more data coming from the receive FIFO still
after detecting the STOP condition. This can be seen from interrupt
status bits DW_IC_INTR_STOP_DET (0x200) and DW_IC_INTR_RX_FULL (0x4).
Perhaps due interrupt latencies the receive FIFO is not read fast
enough, STOP detection happens synchronously when it occurs on the I2C
bus and the DW_IC_INTR_RX_FULL keeps coming as long as there are more
bytes in the receive FIFO.
Fix this by reading the receive FIFO completely empty whenever
DW_IC_INTR_RX_FULL occurs. Use RFNE, Receive FIFO Not Empty bit in the
DW_IC_STATUS register to loop through bytes in the FIFO.
While at it do not test the return code from i2c_slave_event() for the
I2C_SLAVE_WRITE_RECEIVED since to my understanding this hardware cannot
generate NACK to incoming bytes and debug print itself does not have
much value.
Reported-by: Tian Ye <tianye@xxxxxxxxx>
Signed-off-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
---
Hi Tian Ye. I've been testing the i2c-designware-slave.c recently and
discovered these write issues. Your recent patch gave an idea what might
cause them. In my solution I went testing DW_IC_STATUS_RFNE since
according to datasheet it's equivalent to RX_FULL interrupt in case
interrupts are masked. Seems to work here too.
Does this fix the issue you were seeing?
---
drivers/i2c/busses/i2c-designware-core.h | 1 +
drivers/i2c/busses/i2c-designware-slave.c | 12 +++++++-----
2 files changed, 8 insertions(+), 5 deletions(-)
diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
index dbf6bdc5f01b..6d1df28dd93b 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -108,6 +108,7 @@
#define DW_IC_STATUS_ACTIVITY BIT(0)
#define DW_IC_STATUS_TFE BIT(2)
+#define DW_IC_STATUS_RFNE BIT(3)
#define DW_IC_STATUS_MASTER_ACTIVITY BIT(5)
#define DW_IC_STATUS_SLAVE_ACTIVITY BIT(6)
diff --git a/drivers/i2c/busses/i2c-designware-slave.c b/drivers/i2c/busses/i2c-designware-slave.c
index 1eac4f4d5573..295774a69b67 100644
--- a/drivers/i2c/busses/i2c-designware-slave.c
+++ b/drivers/i2c/busses/i2c-designware-slave.c
@@ -180,11 +180,13 @@ static int i2c_dw_irq_handler_slave(struct dw_i2c_dev *dev)
&val);
}
- regmap_read(dev->map, DW_IC_DATA_CMD, &tmp);
- val = tmp;
- if (!i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_RECEIVED,
- &val))
- dev_vdbg(dev->dev, "Byte %X acked!", val);
+ do {
+ regmap_read(dev->map, DW_IC_DATA_CMD, &tmp);
+ val = tmp;
+ i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_RECEIVED,
+ &val);
+ regmap_read(dev->map, DW_IC_STATUS, &tmp);
+ } while (tmp & DW_IC_STATUS_RFNE);
}
if (stat & DW_IC_INTR_RD_REQ) {
--
2.35.1
